I did what you suggested about sliding the bar to turn off earnings from Promoted Content (which should have been the default).

I then checked Related Content / Recommendations back on for pages, posts, index, etc, but nothing is showing. Does it take a while for this to propagate? How is this calculated anyway regarding what is related or not?

edit: some are showing so I guess it takes a while. I still want to know how it chooses the thumbnails (some of these posts or pages do have images, but the default non-image seems to display). And how is this calculated anyway regarding what is related or not?